You may want to review factoring with GCDs and factoring harder polynomials first.

Polynomials can have GCDs and still start with a number once
you've factored it out. For example, consider
6*x*^{2} + 16*x* + 8. The GCD here is 2, so it
factors as 2(3*x*^{2} + 8*x* + 4). But the
polynomial 3*x*^{2} + 8*x* + 4 itself factors,
so the final answer is 2(3*x* + 2)(*x* + 2).